Digital display

ABSTRACT

A digital display device of the line segment type for displaying on a face plate illuminated characters of an alpha-numeric type. The device is generally formed of a housing having a front surface which is covered by a face plate provided with a plurality of slots forming line segments for forming the alphanumeric display to be illuminated. The housing is formed by injection molding and is provided with a plurality of sockets for receiving light producing elements for selectively illuminating a particular arrangement of the slots on the face plate. An arrangement of light emitting diodes of the gallium phosphide or gallium arsenide phosphide types are mounted on a lamp board and assembled with one of the light emitting diodes accommodated within each of the sockets in the housing. A printed circuit board is connected to the lamp board and carries an arrangement of current limiting resistors and driving circuits which are electrically connected to the light emitting diodes for selective energization of a particular diode or combination of diodes. A lens element is carried within each of the sockets and is provided with a raised portion extending into the line segment slots on the face plate so that when the respective light emitting diode is energized the lens will produce uniform illumination of the particular slot.

United States Patent [191 Towne et al.

[ Nov. 4, 1975 DIGITAL DISPLAY [75] Inventors: Herbert Towne, Glen Head;Harold Rapp, Flushing, both of NY.

[73] Assignee: Dialight Corporation, Brooklyn,

22 Filed: Aug. 6, 1973 21 Appl. No.: 385,649

Related US. Application Data [63] Continuation-in-part of Ser. No.268,717, July 3,

1972, abandoned.

[52] US. Cl 340/380; 340/336 [51] Int. Cl. G09f 9/32 [58] Field OfSearch 340/336, 324 R, 324 M, 340/380, 378 R [56] References CitedUNITED STATES PATENTS 3,177,483 4/1965 Scharf et a1 340/336 3,249,9325/1966 Sklaroff 340/336 3,307,175 2/1967 Shill i 340/336 3,432,8463/1969 Jones et al. 340/324 R 3,568,177 3/1971 l-lasler 340/3363,581,307 5/1971 McKim et a1... 340/336 3,641,390 2/1972 Nakamura340/336 Primary ExaminerJohn W. Caldwell Assistant Examiner-Marshall M.Curtis Attorney, Agent, or FirmFrank Trifari; David R. Treacy [57]ABSTRACT A digital display device of the line segment type fordisplaying on a face plate illuminated characters of an alpha-numerictype. The device is generally formed of a housing having a front surfacewhich is covered by a face plate provided with a plurality of slotsforming line segments for forming the alpha-numeric display to beilluminated. The housing is formed by injection molding and is providedwith a plurality of sockets for receiving light producing elements forselectively illuminating a particular arrangement of the slots on theface plate. An arrangement of light emitting diodes of the galliumphosphide or gallium arsenide phosphide types are mounted on a lampboard and assembled with one of the light emitting diodes accommodatedwithin each of the sockets in the housing. A printed circuit board isconnected to the lamp board and carries an arrangement of currentlimiting resistors and driving circuits which are electrically connectedto the light emitting diodes for selective energization of a particulardiode or combination of diodes. A lens element is carried within each ofthe sockets and is provided with a raised portion extending into theline segment slots on the face plate so that when the respective lightemitting diode is energized the lens will produce uniform illuminationof the particular slot.

7 Claims, 11 Drawing Figures Sheet 1 0f 3 US. Patent Nov. 4,1975

US. Patent Nov. 4, 1975 Sheet 2 of3 3,918,053

Fig. 6 Fig.7

US. Patent Nov. 4, 1975 Sheet 3 of3 3,918,053

Fig. If]

Fig. ll

DIGITAL DISPLAY REFERENCE TO PRIOR APPLICATION This is acontinuation-in-part of application Ser. No. 268,717 filed July 3, 1972and now abandoned.

BACKGROUND OF THE INVENTION This invention relates generally to thefield of illuminated display devices and, more particularly to a digitaldisplay device adapted to display upon an opaque face plate, a visualread-out of a particular alphabetic or numeric symbol.

Digital display devices have been in use for many years in variousdisplay systems and widely used in a variety of applications. Some ofthe more common uses of alpha-numeric displays have been in such areasas digital volt meters, tachometers and clocks, computer consoles,stockmarket quotation displays, aircraft and spacecraft consoles invarious military installations. It is desirable in most of these usesthat the display devices have a simple and rugged construction, be easyto install within a console so that installation and replacement may bedone quickly, have low power consumption, low cost factor and mostimportant long life and reliability of the illuminating element. Varioustypes of display devices have been developed in an attempt to meet thesevaried needs. One type of digital display device is the conventionalmonogram design of selectively lighted lucite rods, another type ofdisplay utilizes electro-luminescent coated characters, others are ofthe glow tube display type, still other read-out devices employ a frontface which is entirely covered by a large number of tiny lampsselectively illuminated to outline the desired alpha-numeric character.Also known in the art is the display device utilizing individuallyilluminated light emitting ends of light-conducting material such aslight pipes or light guides wherein the lightemitting ends are arrangedso as to represent a group of segments with which the particularcharacter may be formed. Devices utilizing neon lamps for separatelyilluminating an entire character formed of an individual lamp and otherglow discharge devices have also been suggested. Finally, there is themore popular type of character display to which the present inventionrelates. This is commonly referred to as the segmental system in whichthe display surface typically has seven segments or lines arranged in ageometric pattern substantially defining a figure 8. Selectiveillumination of the various segments can produce any desired numericsymbol from 9. Displays of this type can also include additionalsegments or lines for displaying any desired letter of the alphabet,digit, mathematical symbol, or other fanciful design.

It has been typical in the segmental type of display to produceillumination of each selected segment by means of an incandescent lampplaced directly behind a lamp cover forming the segment to beilluminated. Various opaque materials have been used to block thesurface area surrounding the segment so that only the segmented linewill appear illuminated. A typical arrangement would be to provide aplurality of incandescent lamps within a housing having light socketsfor directing the light toward the particular segment to be illuminated.Devices of this type, although widely used present a number of problems.Incandescent lamps have a limited life which, when they burn out,require replacement and sometimes lead to error in the numeric displaybeing illuminated. Prior art segmental displays have also been deficientin that the illuminations of the various segments are not as uniform asmight be desired and sometimes fail to be adequately or fullyilluminated in areas of bright ambient light conditions.

It is accordingly one object of the present invention to provide aluminous digital display device of the segmental type in which the linesegments are contiguous with one another, which is relativelyinexpensive to produce and assemble and generally overcomes the majordeficiences of the prior art.

In particular, it is an object of the present invention to provide adisplay device of the type described which has an unlimited lifetimenever requiring replacement because of failure of the light producingelements, by utilizing a solid state element as the light producingdevice, thereby maximizing reliability of the read-out device. It is afurther object of the present invention to provide a character displaydevice in which the line segments when illuminated are as uniform aspossible and of sufficient intensity to be clearly visible even in highambient light conditions.

A further object of the invention is to provide a character displaywhich is relatively simple in construction requiring a minimum ofassembly steps and which can easily be fabricated out of molded plasticparts.

SUMMARY OF THE INVENTION The foregoing objects are generally achieved byproviding the device of the present invention which utilizes solid statelight emitting diodes as the line segment illuminating element. Thediodes are electrically and mechanically mounted on a lamp board whichis connected to a printed circuit board carrying appropriate drivingcircuitry for selective energization of one or of a combination ofdiodes. The device comprises a housing formed of molded plastic and isprovided with a socket for receiving and containing each diode. Eachsocket is covered by a lens element which has a raised portion. Thefront of the housing is covered by a face plate which is formed bymolding with seven line segment slots arranged contiguously forming thenumeral 8 when all segments are illuminated. The raised portion of thelens element cove ring the socket extends into the slots so that thelight from an energized diode will uniformly illuminate a particularline segment.

Other objects, advantages and features of the invention will become moreapparent from the following detailed description of the invention inconnection with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective viewof the present invention showing all the constituent parts thereof;

FIG. 2 is a frontal plan view of one face plate showing a plurality ofcharacters which may be arranged in a digital display;

FIG. 3 is a cross-sectional elevational view taken along lines 33 ofFIG. 2;

FIG. 4 is a front view of one embodiment of a lens element used inilluminating a line segment of the character display;

FIG. 5 is a back view of the lens element shown in FIG. 4;

FIG. 6 is a front view of a lens element used in illuminating a decimalpoint character of the display;

'FIG. 7 is a back view of the lens element shown in FIG. 6;

FIG. 8 is a side view of the lens element shown in FIGSJ4 and alongarrow A of FIG. 4;

FIG. 9 is a plan view of the rear of the face plate with lens elements;

FIG. 10 is a side elevational view of the face plate showing anotherembodiment of a lens element used in illuminating a line segment; and

FIG. 11 is a side view of the lens element shown in FIG. 10.

DESCRIPTION OF THE INVENTION In FIG. 1 of the drawing there is shown oneembodiment of a numeric display device in accordance with the-presentinvention for displaying upon an opaque face plate 1, a digital ornumeric symbol. Any digit from 0, l, 2, 3, through 9 may be displayedupon the face plate I by selective illumination of a proper combinationof the line segments formed .in slots 2 through 8. The particulardisplay illustrated in FIG. 1 also includes provision for illuminationof a decimal point through aperture 9. The face plate 1 may be made of anon-reflecting plastic material and preferably dark in color to providemaximum contrast to the illuminated line segments on its surfacemanufactured by injection molding to form the proper combination ofslots and apertures for the desired alpha-numeric display. It has inpractice been found to be of advantage to use a material'commerciallyavailable and known by its trade name Lexan as the plastic materialoutof which the face plate may be fabricated. The face plate '1 formsthe front cover of a housing 10 which is com- 7 formed of an opaqueplastic material (also preferably Lexan) which is easily fabricated byan injection molding process.

The face plate 1 is provided with a plurality of studs 24 arranged forcooperative engagement with partial guide bores 24 on the front surface14 of the housing 10 so as'to provide accurate means for properlyaligning the face plate with the housing. A number of sockets 16, l7,l8, 19, 20,21, 22 and 23 are formed in the housing during the moldingoperation of its fabrication and are designed for receiving and holdingin secure position a lens element, embodiments of which will bedescribed more fully hereinafter. FIG. 1 shows a lens element 40arranged for engagement with slot 2 in a exploded position while thelens element 40 for each of slots 3, 4, 5, 6, 7 and 8 are shown inposition within the slot, only the front surface of the lens beingvisible in 1 the figure. Lens element 41 for illuminating the decimalpoint through aperture 9, is alsoshownin an exploded position. Each ofthe sockets are appropriately shaped so that the lens element, havingone of the designs to be described, may fit complimentary therewith.Sockets l6-22 are arranged to accommodate the lens 40 for illuminationof a line segment. Accordingly each of these sockets has a substantiallycircular crosssectional shape with extended diametric cutouts (such as16 and 16") for receiving the extended end portions 73 of the lens 40.Socket 23 has a quadrangular cross-section al shape in order toaccommodate the lens element 41, shown and described more fullyhereinafter in conjunction with FIGS. 6 and 7. Each socket is arrangedin the housing so as to be located behind a corresponding slot oraperture in the face plate, so that the lens element will cooperativelyengage with the slot on the face plate when the face plate is assembledwith the front surface 14 of the housing. The face plate 1 may bepermanently affixed to the front surface 14 of the housing 10 by placingthe studs 24 within the appropriate partial bores 24' and ultrasonicallywelding the face plate to the housing with the lens elements 40 and 41located in the appropriate socket so that the raised line segmentportion of the lens 40 protrudes into the slots 2 through 8 and theraised circular portion 92 of lens element 41 protrudes into aperture 9.Each of the line segments 2 through 8 and the decimal point 9 is to beilluminated by means of a solid state light source housed within thesockets 16 through 22. The sockets have been designed so as to form areceptacle for receiving the light-producing elements and so as to actas a light restricting cell for separatelyilluminating a particular linesegment upon selective energi-' zation of the appropriate lightproducing element. The interior walls of each of the sockets must besufficiently nonreflecting so that the light produced by the lightelement will travel in as much of an axial direction as is possible.

The light producing elements of the present invention are shown in FIG.1 as being mounted on a printed circuit lamp board 25. The lightproducing elements 26, 27, 28, 29, 30, 31, 32 and 33 are commerciallyavailable light emitting diodes or radiators, referred to as LED;s andformed of a p-n junction diode made of gallium phosphide or galliumarsenide phosphide. It is to be noted that the radiation given off bysome light emitting diodesare not necessarily in the visible range ofwave lengths. However, light emitting diodes that emit visible radiationare essential for the applications of the digital display forming thepresent invention. The gallium phosphide and gallium arsenide phosphidetype diodes are useful in this application.

Each of the LEDs 26 through 33 are electrically connected to the lampboard 25 by leads 34 (see FIG. '3) being soldered thereto at 35. Thelamp board with the light emitting diodes mounted thereon is assembledwith the housing 10 so that the lamp board covers the atright anglesthereto with a portion 44 of the printed circuit board extending beyondthe surface of the board 25. When the lamp board 25 is assembled withthe printed circuit board 43, as shown in FIG. 1, the portion 44 will bein a position to fit within a slot 45 arranged on the rear of thehousing 10. The printed circuittboard with the lamp board attachedthereto may thus be assembled and maintained in proper position withrespect to the housing.

A series of resistors 46, 47, 48, 49, 50, S1 and 52 are mounted on theprinted circuit board. Each of the resistors are electrically connectedin series with a light emitting diode and serve to limit the currentsupply thereto. A current limiting resistor of 200 ohms has been foundto be appropriate. A decoder driver formed by integrated circuit element53 is also mounted on the printed circuit board and electricallyconnected through the resistors to the light emitting diodes forselectively driving them. I

When fully assembled the character display according to the presentinvention as shown in FIG. 1 will comprise the face plate mounted on thefront surface 14 of the housing with the various lens elements containedwithin the sockets 16 through 23 with the raised portions to beilluminated extending into slots 2 through 8 and aperture 9, and withthe light emitting diodes located behind the lenses and contained withina respective socket, lamp board 25 acting as the back surface of thehousing.

FIG. 3 shows in cross-sectional view a digital display in accordancewith the present invention in a fully assembled condition. It can easilybe seen from this figure that the lens elements 40 are arranged withinthe sockets of the housing 10 with the raised portions protruding intothe slotted line segment of the face plate 62. The studs 24 are shown indotted line within the partial bores 24'. The light emitting diodes 27and 31, corresponding to the diodes shown in FIG. 1, are shown in placewithin the sockets l7 and 21 respectively. A space 70 is formed betweenthe housing 10 and the lamp board 25 when the lamp board is in anassembled position with respect to the rear of the housing.

The character display device illustrated in FIG. 1 and described aboveis of the segmental type with the various line segments 2 through 8forming the letter 8 when all segments are illuminated. It should beobvious, however, that other arrangements of line segments are possiblefor the display of alphabetical, arithmetical or other informationalsymbols or characters. Additionally, it may be and frequently isdesirable to arrange a plurality of digital display devices on a consoleor display panel in a line so as to illuminate a multiple digit number.Such an arrangement is shown in FIG. 2 in which four digital displaydevices such as shown in FIG.

l are arranged in line and framed within a single aluminum extrudedhousing 60 and encased by plastic end pieces 61. The face plate 62 ofthe display shown in FIG. 2 comprises a single plastic element moldedwith an appropriate number of line segment slots 63 and decimal pointapertures 64. The display shown here comprises an arithmetic symbol, adigit one and three numeric displays capable of a full range of digitsfrom 0 to 9. Each of the line segments 63 is provided with a lenselement such as shown in FIG. 1 or of the type shown in FIGS. 10 and 11,and each of the decimal point apertures 64 is filled by a lens elementsuch as 41 shown in FIG. 1. Each lens is backed by and to be illuminatedby a separate light emitting diode and appropriate driving circuit withcurrent limiting resistor such as described with reference to thenumeric display of FIG. 1.

It should, of course, be obvious that any arrangement of display devicescan be provided in a display console with a single face plate coveringthe entire area of numeric characters and provided with appropriateslots or apertures for forming any combination of digits or alphabetsymbols.

Referring now to FIGs. 4 and 5, one embodiment of the lens 40, which isintended for use with light emitting diodes of the gallium phosphidetype is shown in enlarged view showing the front and rear surfaces ofthe lens element 40, shown in perspective in FIG. 1. This lens is formedintegrally of two main sections molded of acrylic material and comprisesa first circular section 71 and a raised section 72 having diametricallyextended end portions 73 extending beyond the confines of thecircumference of the circular portion 71. The

width W and length L of the raised portion 72 is designed to fit withinthe slots on the face plate forming the line segments of the characterdisplay. The height H, see FIG. 8, of the raised portion extending fromthe upper surface 74 of the flat circular section of the lens is equalto the thickness of the face plate 1 so that the front surface 82 of theraised portion is flush with or slightly extended beyond the surface ofthe face plate 1 when inserted in the slot, and so that the uppersurface 74 of the circular portion abuts flush with the rear side of theface plate. The rear surface 81 of the circular portion 71 and extendedraised portion 72, which is shown in FIG. 5, will be slightly spacedfrom the emitting surface of the light emitting diode when assembledwithin the socket as shown in the sectional view of FIG. 3. Both therear surface 81 of the circular flat portion 71 and the front surface 82of the raised portion 72 are provided with a ridged surface as shown indetail in FIG. 8 which is a side view taken along arrow A of FIG. 4. Theridges are represented by parallel lines in FIGS. 1, 4 and 5. Lightwhich is emitted from a typical gallium phosphide light emitting diode,represented by rays R, will strike the rear ridged surface 81 of theflat circular portion 71. Upon striking the ridged surface 81 the lightrays will, through the action of reflection and refraction, pass throughand exit the lens at the flat surface 74 of the circular flat portion 71and through the ridged surface 82 of the raised portion 72. Only theraised portion will extend through the slot of the line segment so thatonly the light which passes through the lens exiting at the ridgedsurface 82 of the raised portion 72 of the lens will be visible, theflat surface 74 being blocked by the opaque face plate. The angle abetween adjacent ridges of both the front and rear surfaces of the lensmay be anywhere from to 100. However, it has been found that as a matterof convenience and efficiency in reflecting light a angle would be mostdesirable. The ridged surfaces of the lens elements 40 producesefficient light diffusing effect of the light produced by the lightemitting diode so that the illuminated line segment will appear mostuniform with sufficient brightness against the dark background of theface plate. FIG. 8 shows the ridges as being enlarged anddisproportionate for the sake of clarity however, in practice the depthof the ridges will be much smaller than what is shown so that a greaternumber of ridges will exist on the actual surface of the lens.

FIGS. 6 and 7 are views similar to FIGS. 4 and 5 showing the front andrear surfaces of the lens element 41 used for illuminating the decimalpoint symbol on the character display. This lengs element is fonned of abase portion 92 and a raised circular portion 92 designed to fitcomplimentarily with an aperture such as aperture 9 in the face plate ofFIG. I. The front surface of raised circle 92 and the rear surface 93 ofthe element is ridged in a manner similar to that of lens element 40 soas to obtain the most efficient light diffusing effect from the lightemitting diode. The lens element 42 is designed to fit within socket 23in housing 10 for transmitting the light from light emitting diode 33 toilluminate the aperture 9.

It should be obvious that any other convenient form of slot or aperture,such as a comma or other curved line segment, may be easily produced ina face plate by injection molding. A lens designed to fit such form mayalso be easily produced by molding an acrylic material so that othercharacters may be illuminated upon the face plate of the display.

FIGS. 10 and 11 show another embodiment of the lens 40 which isparticularly useful with light emitting diodes of the gallium arsenidephosphide type. This lens is also formed integrally of two main sectionsmolded of acrylic material comprising a first circular section 101 and araised section 102 having diametrically extended end portions 103extending beyond the confines of the circumference of the circularportion 101. The width W and length L of the raised portion 102 issubstantially the same as the lens shown in FIGS. 4 and so as to fitwithin the slots on the face plate forming the line segments of thecharacter display. The height H, see FIG. 11, of the raised portionextending from the upper surface 104 of the flat circular section of thelens is equal to the thickness of the face plate 1 so that the frontsurface 106 of the raised portion is flush with or slightly extendedbeyond the surface of the face plate 1 when inserted in the slot, and sothat the upper surface 104 of the circular portion abuts flush with therear side of the face plate. The rear surface 105 of the circularportion 101 and extended raised end portion 103 have a stepped surfaceso that the thickness D of the lens decreases toward the center forminga V-shaped recess on the underside of the lens forming a gap from theemitting surface of the light emitting diode when assembled within thesocket. The stepped rear surface 105 of the lens shown in FIGS. and 11provides means for more evenly distributing light being emitted from agallium arsenide phosphide light emitting diode across the front surface106. The light emitting surface of the typical gallium phosphide diodeis significantly broader than that of the gallium arsenide phosphidediode so that the lens shown in FIGS. 4 and 5 will be adequate whengallium phosphide diodes are used as the light emitting source. When thelight emitting source is gallium arsenide phosphide, its light emittingsurface is much narrower and consequently the V-shaped stepped surface105 is preferred.

Light rays X emitting from a gallium arsenide phosphide diode willstrike the stepped rear surface 105 and through the action of reflectionand refraction pass through the lens and exit at flat surface 104 of thecircular flat portion 101 and through the ridged surface 106 of theraised portion 102. Only the raised portion will extend through the slotof the line segment so that only the light which passes throughthelensexiting at the ridged surface 106 of the raised portion 102 of thelens will be visible, the flat surface 104 being blocked by the opaqueface plate. The angle a between adjacent ridges of the front surface ofthe lens is again preferably 90.

FIG. 9 shows the rear surface of face plate with lens 40 of either theembodiments shown in FIGS. 4 and 5 or in FIGS. 10 and 11 in place.

From the foregoing description it can be seen that a character displayof the line segment type has been provided which has the facility ofvirtually unlimited life dueto the use of the solid state light emittingdiodes, and which is both simple in construction and easy to assemble sothat the cost of manufacturing is kept at a minimum. The use of thelenses as described herein produces an illuminating effect which isefficient in transmitting the light from the light emitting diode andadequate even in high light ambient conditions.

While the invention has been described and illustrated with respect to acertain preferred embodiment which gives satisfactory results, it willbe understoodby those skilled in the art, after understanding thepurposes of the invention, that various other changes and modificationsmay be made without departing from the spirit and scope of theinvention, and it is therefore intended in the appended claims to coverall such changes and modifications.

We claim:

1. A character display device of the line segment type comprising adisplay surface having an arrangement of open segments for display ofany numeric and alphabetic symbol against an opaque background uponillumination of a proper combination of segments thus forming thedesired numeric symbol, a plurality of I section having a front surface,said base section being adapted to fit within said socket and saidraised section being adapted to fit within the respective open segment,the rear surface of the base section and the front surface of the raisedsection of said lens being ridged, said front ridged surface of saidlens element being substantially flush with the surface of said displaysurface when said raised section is fitted with the open segment so thatupon energization of a light emitting diode its respective open segmentwill be illuminated by light passing through the lens element having itsraised sec tion fitted within the segment.

2. The character display according to claim 1.

wherein said open segments are straight line slots, said slots beingarranged contiguously in a figure 8 pattern so that any numeric digitmay be displayed by illumination of a proper combination of slots, theraised section of said lens element for said slots being substantially:

elongated formed in the shape of a straight line so as to fitcomplimentarily within said slot.

3. The character display according to claim 1 wherein at least one ofsaid open segments is a circular.

aperture so that upon illumination thereof a decimal point characterwill be displayed, the raised section of l said lens element for saidcircular aperture being formed substantially in the shape of a circle soas to fit complimentarily within said aperture.

4. The character display according to claim 1 wherein said ridges, havean included angle of approximately 5. A character display device of theline segment type comprising a display surface having an arrangement ofopen segments for display of any numeric and alpha betic symbol againstan opaque background upon illumination of a proper combination ofsegments thus forming the desired numeric symbol, a plurality of socketsarranged behind said display surface, one of said sockets being arrangedsubstantially behind each of said open segments, a light emitting diodeof the p-n junction type for producing visible light upon electricalenergization thereof carried within each of said sockets forillumination of its respective open segment when said diode is caused toproduce visible light, a lens element for even and uniform distributionof the visible light produced by the light emitting diodes, said lenselement comprising a base section and a raised section, the base sectionhaving a rear surface and the raised section having a front surface,said base section being adapted to. fit within said socket and saidraised section being adapted to fit within the respective open segment,the front surface of the raised section of said lens being ridged, saidfront ridged surface of said lens element being substantially flush withthe surface of said cluded angle of approximately I

1. A character display device of the line segment type comprising adisplay surface having an arrangement of open segments for display ofany numeric and alphabetic symbol against an opaque background uponillumination of a proper combination of segments thus forming thedesired numeric symbol, a plurality of sockets arranged behind saiddisplay surface, one of said sockets being arranged substantially behindeach of said open segments, a light emitting diode of the p-n junctiontype for producing visible light upon electrical energization thereofcarried within each of said sockets for illumination of its respectiveopen segment when said diode is caused to produce visible light, a lenselement for even and uniform distribution of the visible light producedby the light emitting diodes, said lens element comprising a basesection and a raised section, the base section having a rear surface andthe raised section having a front surface, said base section beingadapted to fit within said socket and said raised section being adaptedto fit within the respective open segment, the rear surface of the basesection and the front surface oF the raised section of said lens beingridged, said front ridged surface of said lens element beingsubstantially flush with the surface of said display surface when saidraised section is fitted with the open segment so that upon energizationof a light emitting diode its respective open segment will beilluminated by light passing through the lens element having its raisedsection fitted within the segment.
 2. The character display according toclaim 1 wherein said open segments are straight line slots, said slotsbeing arranged contiguously in a figure 8 pattern so that any numericdigit may be displayed by illumination of a proper combination of slots,the raised section of said lens element for said slots beingsubstantially elongated formed in the shape of a straight line so as tofit complimentarily within said slot.
 3. The character display accordingto claim 1 wherein at least one of said open segments is a circularaperture so that upon illumination thereof a decimal point characterwill be displayed, the raised section of said lens element for saidcircular aperture being formed substantially in the shape of a circle soas to fit complimentarily within said aperture.
 4. The character displayaccording to claim 1 wherein said ridges have an included angle ofapproximately 90*.
 5. A character display device of the line segmenttype comprising a display surface having an arrangement of open segmentsfor display of any numeric and alphabetic symbol against an opaquebackground upon illumination of a proper combination of segments thusforming the desired numeric symbol, a plurality of sockets arrangedbehind said display surface, one of said sockets being arrangedsubstantially behind each of said open segments, a light emitting diodeof the p-n junction type for producing visible light upon electricalenergization thereof carried within each of said sockets forillumination of its respective open segment when said diode is caused toproduce visible light, a lens element for even and uniform distributionof the visible light produced by the light emitting diodes, said lenselement comprising a base section and a raised section, the base sectionhaving a rear surface and the raised section having a front surface,said base section being adapted to fit within said socket and saidraised section being adapted to fit within the respective open segment,the front surface of the raised section of said lens being ridged, saidfront ridged surface of said lens element being substantially flush withthe surface of said display surface when said raised section is fittedwith the open segment, the rear surface of the base section having amultiplicity of steps forming a concave stepped surface so that uponenergization of a light emitting diode its respective open segment willbe illuminated by light passing through the lens element having itsraised section fitted within the segment.
 6. The character displayaccording to claim 5 wherein said stepped rear surface is V-shaped. 7.The character display according to claim 5 wherein said ridges of thefront surface have an included angle of approximately 90*.